Catalytic polymerization process



Patented Oct. 20, 1953 CATALYTIC POLYMERIZATION PROCESS Gaetano F. DAlelio, Pittsburgh, Pa., assignor to Koppers Company, Inc., a corporation of Delaware No Drawing. Application September 28, 1948, Serial No. 51,635

9 Claims. 1

This invention relates to a. process for the polymerization of acrylonitrile and methacrylonitrile. More specifically, it relates to a process using a new catalyst-combination for the polymerization of acrylonitrile and methacrylonitrile.

Polymers of these compounds having substantial amounts of residual monomer and low-molecular-weight polymers therein usually have certain undesirable properties, such as high-shrinkage in boiling water, low resistance to heat-distortion, potential discoloration due to oxidation of monomers, and crazing due to escape of volatile or fugitive materials. For these reasons, there is considerable interest in producing monomer-free polymers of acrylonitrile and methacrylonitrile. In addition, it is desirable to have a consistent and easily-controllable method for producing such polymers having high average molecular weights.

It has now been found that improvements in the polymerization of acrylonitrile and methacrylonitrile can be obtained by employing in the polymerization of these compounds a catalyst-combination consisting of a benzoyl peroxide and at least one other organic peroxy compound of the class consisting of tertiary-butyl perbenzoate, ditertiary-butyl diperphthalate and 2,2-di-(tertiary-butyl-peroxy)-butane, and heating at a temperature between about 25 C; and about 80 C. until at least about 60 percent conversion of monomer to polymer has been effected, and then heating at a temperature between about 85 C. and about 125 C. until substantially complete polymerization has been effected.

The term a benzoyl peroxide is intended to include benzoyl peroxide and those derivatives of benzoyl peroxide having one or more chloro. bromo, fluoro, alkoxy (i. e., methoxy, ethoxy, propoxy and butoxy), alkyl (i. e., methyl, ethyl, propyl and butyl), benzo, or carboperoxy groups attached to the aromatic nucleus. Such substituents may be attached to either or both of the aromatic nuclei of the benzoyl peroxide. This class includes such peroxides as chlorobenzoyl, bromobenzoyl, fluorobenzoyl, alkoxy-benzoyl, a1- kyl-benzoyl, phthaloyl and naphthoyl peroxides.

The use of mixtures of organic peroxy compounds as polymerization catalysts is not new in itself. Trigger-systems have been known wherein a small amount of a strongly active peroxide, such as cyclohexyl hydroperoxide, sets off a slow peroxide, such as tertiary-butyl hydroperoxide. Such systems permit the use of an otherwise slow catalyst to give the desired degree of polymerization or cure in a short time without the increase in peak temperature or exotherm otherwise necessary. More recent disclosures have shown the use of a mixture of a relatively heat-sensitive organic peroxide, such as benzoyl peroxide, with certain relatively heatstable peroxides, such as tertiary-butyl hydroperoxide, di-tertiary-butyl peroxide, l-hydroxycyclohexyl-hydroperoxide-1, etc., first at a temperature below C. and then above C. The prior art catalyst-combinations have not been found suitable for the purposes of the present invention.

The decomposition characteristics or free-radical formation of a particular peroxy compound are usually somewhat dependent on its surroundings, i. e., on the monomer or other peroxy compound admixed with it. For example, the decomposition temperature of a peroxy compound by itself may be quite different from that exhibited under the influence of a monomer or other peroxy compound. Moreover, these characteristics may be varied by the type of monomer or peroxy compound. Furthermore, the selection of peroxy compounds to use in combination with a particular peroxide, such as benzoyl peroxide, may often be dependent on the type of polymerization system to be used. It has now been found, however, that the particular catalyst-combinations of this invention operate very satisfactorily and may be used in the improved process of this invention.

The effective proportions of catalysts in the catalyst-combinations and effective proportions of catalyst-combination to monomer are dependent somewhat on the amount of residual monomer permissible in the polymer products, the specific catalyst-combination, the particular monomer or monomers, the type of polymerization system, the temperatures, the time of heating, and the effect of plasticizers, emulsifying agents, diluents, etc., present in the polymerization mixtures. Although the influence of many of these factors often must be determined in each particular instance, certain generalizations may be made. For example, it may be stated as generally true that low temperatures in the first heating stage over relatively long periods may permit more enicient use of the primary catalyst, i. e., the benzoyl peroxide, so that les secondary catalyst, such as tertiary-'butyl perbenzoate, etc., may be required. Moreover, the required amount of secondary catalyst may also be reduced by the use of the lowest temperatures possible in the effective range for the second heating stage over relatively long periods, thereby obtaining pos- 2,656,341 3 4 sibly more efficient use of the secondary catalyst monomer, p y r or m x es the of- Such than possible at higher temperatures. In addicoalescence may result in the precipitation tion, complete polymerization usually may be fao r 1' po ym r from the System For this vored by a relatively high temperature at the end reason it has generally been found necessary to of the heating schedule. Thus, it is obvious that e operate suspension polymerization systems below determinations of the limitations .for efiective certain temperatures until at least a definite deranges *of catalyst. ratios a y t c0mbinaifgre of'polymerizationror conversion'trom monotion concentrationsare dimcult' without specific mer'to polymerhas been effected. Inthe case reference to the temperatures and other condiof acrylonitrile and methacrylo the tions to be used. Moreover, the use of the low fl 'fierature is ge e lly desirably maintained below temperatures referred to abovewillmnecessitate wabout.80" iCl unti1.at least about 60 per e t 0 nlonger heating periods, which is an important O' po ymer has been effected. Once the cost factor and must also zbeiconsidered inrdeconversronhasreached this stage, the temperatermining the conditions tde be;tappliedctomany tureumay ebe ncreased with considerably reduced particular polymerization. likelihood of coalescence or precipitation. It can In order to make easier .eomparigone gfjhe be understood,..therefore, that the active ranges catalytic eiiiciencies of various peroxides eper- 'of;the catalyst-combinations of this process are esters and perethers with each other and with 7911 ed t0 the quirements of susp o various combinations of each other,equivalent Polymerization y e s T01 ae y fl it le and weights of these compounds may be determined 0 methacrylonitrile, Si t first he ng sta -inthe following-manner.-$irst, adetermination marr es the -pO y n'-Pastthe "-s l --isi-made-of the-equivalent weight of benzoyl-perp se or -that.-; phase of athe pe y t om' t i t tii hv-required per unit weight-of which theesystem' is very susceptible to "coales- :monomer to give;'by.a particular'heating sched- "681109;findthehigher per ure Ofthesecond --ule,.-: aw olymer-havin a relative 'viscosity of 2r heating stage ds in the complet on of the polyabout 2.5;18, =f -om to Then t .mer-izationa-fter thepossibility of coalescence-has .equivalent weight-of a=se'condary" catalyst, i;- e-, wthus'meenweducedsince'flle'temperaturefof tertiary-butyl; perbenzoate,- etc" isdetermined d'heatingwstagemay-be near or-above .awhich will givezfrom the same monomer; arpolyr=P f rylonitrile and methacry- -mertof: the "same-relative:viscosity by use-of the-" tr le; .the.- second heating stagewor'possibly :same-heatingschedule; Thereafter; the amounts mthrthe first anisecondheatmgStages maybe of catalyst or mixtures of catalyst to be used for conduetedinenclosed-reactors to prevent loss-of suchaheating schedule can bersel'ectedi accordmonomerring to'these equivalents-"For exampleyan'so-zo Although t pp t m f' p e p lmixture of :benzpyl eroxide and tertiary-but esshas beenrsespeciallyadvantageous in suspenperbenzoate contains-these*-catalysts in respec sion polymerization;- itris ralsovefiective' -in'-pro- -tiveaamountswihaving a 'ratio' corresponding to "ducing improvementsdn the p tion Df r ie f BG'percent .Of' the equivalent-weight :acrylonitrile and methacrylonitrile in mass; solu- ..of. benzoy}..peroxideatoqoqper cent- 0f the-equiva tion and emulsion systems. The difliculty in prot weight t t c e n rmQl3lI1g:-=Subsl33nfi&1ly* complete polymerization is As" previously :-mentioned, a." determination of encounteredin 'these polymerizationsystems; 4.1 -1 it q n-roperativerramountsof catalyst for well as.- .-in-;-suspension polymerization systems, sthe process of this: inventionis rather 'difficult andihe'pmcessiofihis'inventioll s v rbecausei :of'the' numerous "factors involved. -tIn 'f lfi 'efiecting er' pereentage'converaddi-tion, the-rlower limit .onthe:efiectivefrange-. Systems. e particular "for-.- amounts of catalyst combination'zsnecessary U u pension polymerizationw of 'raerylonitrile: with for: theqoperation of'this': invention "will" vary acercent benZOyIPerOXideand p r cent -cording-to the ratio ofzthe'catalysts'in-the comk-tertieryrbutyl perbenzoatebasea on the"weight binationj'so that ydetermination of such -lower monomer; d -7 0 0mer to water-ratio, fiimitlhas.mtleimeaningaor 5 .conducted;.-in capped bottle agitated' by au'ocku h catalyst-combination the ratio op-equiv ..-1ngimechanism=while.immersediina:controlled- *lBIIt' WBightST 'of primarymcatalyst td:secondary a ure bath-:at 60 .C.-f0r+' 2 h F catalystrshouldi-be atFIeasirFabOut QW-I; :advanif-0rLhovrsendrlfiili Offer 2 rsreave very 'tageouslyvat'least about 98:2; for. practicalmphard y r beads. --eration. "Nevertheless:asizzpointedout before, i I he suspen i p ym r z tion procednre'siised c lower iimitseon a secondary zcatalystrx ointhe experiments. disoussedaherein followed fthat 'zdenendent to :some'extent-rom the; heatingscheddescribeiiiby 1M; m, tin. his copendins -ule-employedrandFinsome:ca'sespsmaller"amounts pncationst Serial N055 1786,6555 nOWPRtBmFNO- of-secondary 31331 511 ja re som tim s rmi sibl 2;594,913-, .%and 'Z86;656-,.-now=. abandoned; both api withlonger heatingfinone' or both of the heating *Plicafiions hevmg d r-18, :1947, tages; or:wj thaghigh --1; t :"F and a'ssigngdtdthe same'assignee :as the 'presawpractical viewpointfthe upper ..-1i it rt ent applic'ation. iThis procedure involves the'ruse proportionfof secondary' catalyst' is' determined a watereinsoluble'imetalphosphate; eferab :chiefiy-by-the cost-factor. i In suspension .po1y oi sube-micronic particle'size, together with a very pmerizations,"however.this upper also a 5 .smallwamount of a surface active'agent. How- ::determined 1 somewhat "by the fact that the presver, he present invention? 1101? limited :ence of-ithe secondaryxcatalyst"inirlarge propor- Such ProcessesSuspensionpmymeriZatiOni-but mans} may result in poorecomfol Of-tm? suspem :may=- -be usedwith any suspension polymerizati'on =si0n-p0lymerizati0n and: may therebycause pre- "processciDitationnorlumD- formationj th h .co-a'lgulai :Generallyitheflower. limitforthetemperature .tion f, polymer range? or the firstheating stage :is 'that tempera- :The process oil-this invention' is especially aptul'ei t y peroxide ype catalys i licable. to.suspensionpolymerizatiomsystems. 'In *will pr m0 e ppreciable rate of pol'yme'riza- .such. systems. considerable-rprecaution must be tionlunder the infiuencepf monomer and'o'ther taken. to prevent coalescencezof the} globules'rsof peroxyficompoundsfi and underother conditions of polymerization. The substituted benzoyl peroxides, in general, have lower decomposition temperatures than benzoyl peroxide itself and may usually be employed to good advantage in promoting polymerizations at temperatures of 25 C. or higher. It has been found that the catalyst-combinations of this invention operate satisfactorily in a temperature range of about 25-80 C. for the first heating stage, advantageously about 50-80 C. when benzoyl peroxide itself is used. For the second heating stage a temperature range of about 85-125 C. has generally been found suitable. As pointed out before, however, there are numerous factors which may affeet the polymerizations; and since it is, therefore, difficult to set the temperature limits without some indication of the other conditions involved, it must be understood that th temperature limits may vary somewhat according to these conditions.

Acrylonitrile and methacrylonitrile may be polymerized, according to the process of this invention, alone, in mixtures with each other, or in mixtures containing one or both and one or more other copolymerizable ethylenic compounds. It is sometimes advantageous that the acrylonitrile and methacrylonitrile be in preponderance, especially when the copolymerizable ethylenic compound is one usually slightly reluctant to copolymerize with the acrylonitrile and methacrylonitrile.

Illustrative examples of the copolymerizable ethylenic compounds which may be copolymerized with acrylonitrile and with methacrylonitrile in accordance with the practice of this invention are: vinyl aryls, such as styrene, vinyl naphthalenes, etc., and their nuclear-substitution products, for example, those having one or more of the following substituent groups, halogen, such as chloro, fluoro, etc., for example, monochloro-styrene, i. e., ortho-, metaand para-chloro-styrenes, dichloro-styrenes, trichlorostyrenes, fluorostyrenes, vinyl chloro-naphthalene, p-chloro-p-vinyl-diphenyl, etc., hydrocarbon groups, such as alkyl, alkenyl, and, arylalkyl, alkyl-aryl, cycloaliphatic, etc., for example, monoand di-methyl-styrenes, ethyl-styrenes, isopropyl-styrenes, vinyl methyl-naphthalenes, divinyl benzenes, partial polymers of divinyl benzenes, phenyl-styrenes, phenethyl-styrenes, tolyl-styrenes, cyclohexyl-styrenes, etc., cyano, for example, monoand dicyano-styrenes, substituted alkyl groups, such as trifluoromethyl, cyanomethyl, alk-oxyalkyl, carboxyalkyl, etc., for example, trifluoromethyl-styrenes, cyanomethylstyrenes, methoxy-methyl-styrenes, acetoxyethyl-styrenes, etc.; the vinyl halides, e. g., vinyl chloride, vinyl fluoride, the vinylidine halides, e. g., vinylidene chloride, vinylidene fluoride, etc.; the amides of acrylic, alpha-methacrylic, alphachloroacrylic, beta-cyanoacrylic acids, etc.; the nitrile derivatives of alpha-chloroacrylic, betacyanoacrylic acids, etc., e. g., a1pha-chloroacrylonitrile, fumaro-nitrile, etc.; methylene-malonic esters, the mono-alkyl esters and the dialkyl esters, e. g., the monomethyl and the dimethyl esters, the dipropyl esters, etc: allyl derivatives, e. g., acrolein, methacrolein, allyl methyl ketone, allyl ethyl ketone, allyl chloride, allyl methyl ether, allyl ethyl ether, allyl butyl ether, allyl phenyl ether, allyl acetate, allyl propionate, allyl acrylate, methallyl acrylate, diallyl phthalate, diallyl oxalate, diallyl succinate, diallyl ether, diallyl ketone, dimethallyl ketone, etc.; acrylic, methacrylic, alpha-chloroacrylic,

beta-cyano-acrylic, maleic, fumaric, citraconic' acrylate, propyl methacrylate, methyl alpha-- chloroacrylate, methyl beta-cyano-acrylate, phenyl beta-cyano-acrylate, dimethyl' maleate, dimethyl fumarate, diethyl maleate, diethyl fu-' marate, di-isopropyl maleate, dimethyl citraconate, diethyl citraconate, etc.; vinyl ethers,

e. g., divinyl ether, vinyl methyl ether, vinyl phenyl ether, etc.; vinyl ketones, e. g., divinyl ketone, vinyl methyl ketone, acrylophenone, etc. Acrylonitrile or methacrylonitrile or mixtures thereof can be copolymerized with anycop'olymerizable ethlenic monomer such as the above or with a mixture containing any number of such monomers.

The process of this invention has been found' especially useful in the preparation of plasti- Normally the cized or lubricated polymers. presence of a plasticizer in a polymer causes an increase in the shrinkage and a lowering of the heat-distortion temperature. However, the improvements in these thermal properties effected by the present invention make it possible to produce plasticized or lubricated acrylonitrile and methacrylonitrile polymers'having' a greater resistance to shrinkage and to heat-distortion than usually found in plasticized acrylonitrile and methacrylonitrile polymers prepared with ben' zoyl'peroxide alone.

The distinction between plasticizers and lulapping of the particular function of a great many compounds used to promote ease of flow, and in order to facilitate reference to these com-- pounds, the term plasticizer is'used broadly hereinafter to include both plasticizers and lubricants.

Various types of plasticizers are suitable for use in the practice of this invention. Included among these are: fatty acid ester plasticizers, such as butyl stearate, beta-butoxyethyl stearate, methyl oleate, amyl oleate, cyclohexyl stearate; esters of dicarboxylic aliphatic acids, such as dicapyryl sebacate, etc.; aryl ether and ester plasticizers such as dimethyl phthalate, dibutyl phthalate, diamyl phthalate, dibenzyl maleate, beta-phenoxy-ethyl benzoate, beta-(3- chloro-2-xenoxy)-ethyl levulinate, beta-ethoxy ethyl 2-chloro-phenoxy acetate, beta-butoxyethyl phenoxy-acetate diaryl ether derivatives such as chlorinated diphenyl ether and cyclohexyl chlorinated diphenyl ether, aryloxyalkyl On the other hand, lubricants are,

preciably retard the polymerization. The amount of plasticizer to be added usually depends on a number of factors, which include the efliciency of the particular plasticizer, the degree of plasticity desired, etc. In general, however, at least about 0.2-0.5 per cent plasticizer is added before any noted change in flow or plasticity is accomplished.

What is claimed is:

-1; The process of polymerizing a polymerizable mass containing a compound of the class consisting of acrylonitrile and methacrylonitrile as the onlypolymerizable constituent thereof, intimately mixed with a catalyst-combination consisting of tertiary butyl perbenzoate and a benzoyl peroxide of the class consisting of henzoyl. peroxide and its chloro, bromo, fluoro, alkoxy, alkyl, benzo and carboperoxy nucleare substituted derivatives, by heating the polymerizable mass at a temperature between about C. and about C. until at least about per cent conversion to polymer has been effected, and subsequently at a temperature between about 85 C. and about 125 C. until substantially complete polymerization has been efiected.

2. The process of polymerizing a polymerizable mass containing a compound of the class con-' sisting of acrylonitrile and methacrylonitrile as the only'polymerizable constituent thereof, intimately mixed with a catalyst-combination consisting, of benzoyl peroxide and tertiary-butyl perbenzoate by heatin the polymerizable mass at a temperature between about 25 C. and about C. until at least about 60 per cent conversion to polymer has been efiected, andsubsequently at a temperaturebetween about C. and about C. until substantially complete polymerizationhas been efiected.

- 3. The process of claim 2, in which the polymerization is conducted in a suspension polymeriza-tion system. v

mass containing acrylonitrile as the only polymerizable constituent thereof intimately mixed:

with a catalyst-combination consisting of. benzoyl peroxide'and tertiary-butyl perbenzoate by heating the polymerizable mass at a temperature between about 25 C. and about 80 C. until at least about 60 per cent conversion to polymer has been efiected, and subsequently at a temperature between about 85 C. and about 125 C. until substantially completepolymerization has been effected.

7. The process of polymerizing a polymerizable mixture containing methacrylonitrile as the only polymerizable constituent thereof and a catalystcombination consisting of benzoyl peroxide and tertiary-butyl perbenzoate by heating the poly-. merization mixture at a temperature betweenabout 25 C. and about 80 C. until at least about 60.-per cent conversion to polymer has been effected, and subsequently at a temperature :be--

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,426,476 Vaughan et a1 Aug. 26, 194? 2,426,719 Watkins Sept. 2, 1947 2,444,655 Kroeker et a1 July 6, 1948' 2,455,569 Dickey Dec. '7, 1948 2,504,082 Neher et a1 Apr. 11, 1950 ,13 Jacobson Aug. 15, 1950 FOREIGN PATENTS Number Country Date 604,544 Great Britain July 6, 1948 OTHER REFERENCES Perry et al., article in Modern Plastics, No.- vember 1947, pages 134-136, 216, 218, 220, and 222. 

1. THE PROCESS OF POLYMERIZING A POLYMERIZABLE MASS CONTAINING A COMPOUND OF THE CLASS CONSISTING OF ACRYLONITRILE AND METHACRYLONITRILE AS THE ONLY POLYMERIZABLE CONSTITUENT THEREOF, INTIMATELY MIXED WITH A CATALYST-COMBINATION CONSISTING OF TERTIARY BUTYL PERBENZOATE AND A BENZOYL PEROXIDE AND ITS CHLORO, BROMO, FLUORO, ALZOYL PEROXIDE AND ITS CHLORO, BROMO, FLUORO, ALKOXY, ALKYL, BENZO AND CARBOPEROXY NUCLEARSUBSTITUTED DERIVATIVES, BY HEATING THE POLYMERIZABLE MASS AT A TEMPERATURE BETWEEN ABOUT 25* C. AND ABOUT 80* C. UNTIL AT LEAST ABOUT 60 PER CENT CONVERSION TO POLYMER HAS BEEN EFFECTED, AND SUBSEQUENTLY AT A TEMPERATURE BETWEEN ABOUT 85* C. AND ABOUT 125* C. UNTIL SUBSTANTIALLY COMPLETE POLYMERIZATION HAS BEEN EFFECTED. 